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Physics Astrophysics Earth and Planetary Astrophysics

astro-ph.EP Watch Earth and Planetary Astrophysics

Monday 24 August

Earth and Planetary Astrophysics

Intra-system Uniformity through Planetary Embryo Accumulation

Donald Liveoak and Fred C. Adams

Intra-system uniformity is a key trend in observed exoplanet systems. Understanding the physical mechanisms which sculpt planetary systems into uniform or non-uniform configurations will help constrain theories of planet formation. Motivated by previous work showing that intra-system uniformity is a natural consequence of proto-planetary systems dissipating energy and settling into lower energy configurations, this paper explores the energy minimization hypothesis using $N$-body simulations. We find that the accumulation of planetary embryos through inelastic mergers generally dissipates a substantial fraction of the system energy, but the systems do not always reach the global energy minimum. Analytic predictions indicate that planetary pairs have nearly equal masses in their lowest energy state when the total mass falls below a mass threshold. With larger total mass, one member of the pair tends to accrete most of the mass. Our numerical simulations show that pairs with masses above the threshold tend towards non-uniformity, but that the full realization of the effect occurs at a larger mass scale, a factor of $\sim4$ above the threshold. In any case, however, the low-mass planet pairs are generally more uniform than pairs with high mass, in agreement with previous work. Finally, we compare our results to the observed sample of exoplanets and find overall agreement.
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Earth and Planetary Astrophysics

Potential sublimating exocomets around the young star PDS 70

Aline Novais, H. Jens Hoeijmakers, Alexandra Stockwell Murphy et al. (+4 more)

Recent observations by the James Webb Space Telescope (JWST) have indicated the presence of water in the inner regions of the disc around the young protostar PDS 70, but the origin of this water remains unclear. Here we report the discovery of variable absorption lines of neutral sodium in archival High Accuracy Radial velocity Planet Searcher (HARPS) spectra of PDS 70. These lines vary strongly and stochastically on a daily basis, in amplitude, number, and radial velocity. Our measurements indicate that this gas tends to be optically thick, and partially cover the stellar disc, meaning this fast-moving gas is often spatially confined. We explore several hypotheses for the origin of these lines, and conclude that a likely source of the observed sodium is sublimation of planetesimals that transit the star on highly elliptical orbits, reminiscent of the exocomet phenomenon seen in other seen in other extrasolar systems. These sublimating exocomets could play a role in sourcing the previously observed water in the inner, terrestrial-planet forming region of the PDS 70 system.
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All authors Aline Novais, H. Jens Hoeijmakers, Alexandra Stockwell Murphy, Bibiana Prinoth, Anders Johansen, Klaudia Jaworska, Luan Ghezzi

Earth and Planetary Astrophysics · Cross-listed from astro-ph.SR

Solar chemical composition

A. M. Amarsi and N. Grevesse

The Sun is one of the fundamental benchmarks in astronomy, and there is ever growing interest in precise and accurate determinations of its chemical composition. We present the current state-of-the-art in spectroscopic determinations of the solar elemental abundances, that now routinely employ three-dimensional (3D) radiative-hydrodynamic simulations of the solar photosphere and post-processing in non-local thermodynamic equilibrium (non-LTE). We critically review the recent literature and present recommended present-day and protosolar abundances of the 83 long-lived elements, and discuss their implications vis-à-vis primitive meteorites, helioseismology, neutrino fluxes, and the Solar Modelling Problem.
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Earth and Planetary Astrophysics

Korean Space Collision Environment Assessment Framework Based on 3D-Cell Model

Jaewoo Kim, Minchan Song, Jinsung Lee et al. (+6 more)

Space situational awareness (SSA) requires purpose-matched models across spatial, temporal, and fidelity scales. Building on our previously reported three-dimensional (3D) cell formulation and implementation, this study establishes a reproducible, resolution-aware, catalog-conditioned framework for macroscopic assessment of the low Earth orbit (LEO) collision environment. The framework maps supplied catalog or scenario populations to time-averaged spatial density and target-specific impact metrics while retaining individual-object information. Using a 2025 Space-Track snapshot, we evaluate radial, declination, and right-ascension resolution sensitivity and computational performance for six targets, including two Korean space assets. Normalized expected impact counts range from 0.615 to 1.599 and vary nonmonotonically; for a synthetic 500-km circular target, the result at a 0.25-km radial width is 38.5% below the 10-km reference. Runtime and memory show direction-dependent trade-offs. Ten annual snapshots show catalog growth from 15,723 objects in 2016 to 28,540 in 2025 and a 7.86-fold increase in the 500-km target metric, driven primarily by Starlink, other payloads, and unknown/TBA records. In a conditional stress test of the proposed 998,240-satellite SpaceX Orbital Data Center population, exact annual probabilities of at least one impact reach $3.75\times10^{-3}$ and $1.48\times10^{-3}$ for the 700-km and 1,000-km targets. The framework provides a reproducible, resolution-aware basis for catalog-conditioned environment monitoring, comparative scenario assessment, and prioritization of cases for higher-fidelity follow-up analysis.
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All authors Jaewoo Kim, Minchan Song, Jinsung Lee, Jiwoong Yu, Hosik Kam, Jung Hyun Jo, Eun-Jung Choi, Jin Choi, Jaemyung Ahn

Earth and Planetary Astrophysics

Thermochemical constraints on a primordial-origin of gas-rich debris disks

H. Mitani, W. Ooyama, R. Nakatani et al. (+2 more)

Recent observations have revealed gas-rich debris disks around intermediate-mass stars at ages of tens of Myr. The origin of this gas remains unclear: it may be primordial, retained from the protoplanetary phase, or secondary, released from volatile-rich solids. Secondary-origin models reproduce CO emission but often overpredict neutral carbon. Recent observations and disk-evolution models suggest that primordial gas may survive longer than previously assumed, motivating thermochemical tests of the primordial-remnant scenario. We test the previously unexplored possibility that primordial-origin disks satisfy the observational constraints on gas-rich debris disks. Specifically, we determine under what conditions a disk around a $2\,M_{\odot}$ star reproduces substantial CO, low CI/CO ratios, and weak HCO+ emission consistent with current non-detections. We post-processed 20-40 Myr structures from 1D disk-evolution models with Cloudy, varying irradiation geometry, dust-to-gas mass ratio (DTG), and cosmic-ray ionisation rate. In the dust-poor models (DTG $=10^{-4}$), CO remains optically thick around $R\sim100$~au. The models yield low disk-integrated CI/CO mass ratios. Our model produces CO radial intensities of the observed order of magnitude, but its CI-emitting region is more extended than observed. The standard CR model overproduces HCO+, whereas the weak CR model brings its predicted luminosity within current observational limits. These results demonstrate that a primordial origin remains chemically viable for CO-rich debris disks. The main remaining tension is the excessive radial extent of the CI emission, although it may reflect our simplified modelling. Further testing of the primordial-origin scenario will require multidimensional, self-consistent modelling, spatially resolved CI observations, and deeper searches for HCO+.
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All authors H. Mitani, W. Ooyama, R. Nakatani, R. Kuiper, T. Hosokawa

Earth and Planetary Astrophysics

On the formation of retrograde S-type planets in binaries with a polar circumbinary disk

Cheng Chen, Philip J. Armitage, C. J. Nixon et al. (+2 more)

Retrograde S-type planets have been observed in several binary systems, yet their formation pathway remains poorly understood. With high-resolution hydrodynamic simulations, we demonstrate that a polar circumbinary disk around an eccentric, unequal-mass binary can form and sustain a retrograde mini disk around the primary star. This provides a direct in-situ formation channel for retrograde S-type planets. The mini disk forms via a sub-Keplerian accretion stream that is slightly misaligned from the polar disk. The mini disk initially undergoes von Zeipel-Kozai-Lidov (ZKL) oscillations, driving coupled eccentricity and inclination evolution. Rather than oscillating indefinitely, the inner mini disk evolves past the critical ZKL inclination, decouples from the outer disk, and settles into a stable retrograde orbit. This evolution is sensitive to numerical resolution: the retrograde configuration is absent in previous lower-resolution simulations, where the mini disk accretion timescale is too short to sustain ZKL-driven evolution. For a higher disk viscosity, the mini disk remains near-polar due to a shorter accretion timescale. Since protoplanetary disks typically have low viscosity, our results suggest that retrograde S-type planets can form in-situ from retrograde mini disks around polar circumbinary disks, and their occurrence rate may be higher than currently estimated.
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All authors Cheng Chen, Philip J. Armitage, C. J. Nixon, Stephen H. Lubow, Rebecca G. Martin

Sunday 23 August

Earth and Planetary Astrophysics · Cross-listed from physics.ao-ph

Elveslocation: A new approach for studying thunderstorm atmosphere

S. A. Sharakin and R.E. Saraev

Thunderstorm electrical discharges, which vary in their type of initiation and development (including compact intracloud discharges and initial breakdown pulses), also manifest differently as recorded electromagnetic signals in both the radio and optical ranges. A unique ionospheric optical imprint of a discharge is an ELVES - a sub-millisecond glow at altitudes around 90 km with a characteristic spatiotemporal pattern in the form of an expanding ring, reaching a diameter of several hundred or even a thousand kilometers. The position of the elve, its expansion velocity, the azimuthal and radial distribution of the glow intensity (and their temporal dynamics) contain information about the location and orientation of the discharge, as well as its current function. This information is most fully represented in the data recorded by orbital detectors of dynamic images with a wide field of view and microsecond temporal resolution, such as the TUS and Mini-EUSO. Recovering the parameters of a discharge from orbital detector data is associated with solving a complex inverse problem, since the phenomenon of interest is mediated by several processes, including the interaction of the discharge's electromagnetic pulse with the ionosphere and the non-trivial instrument response function of the detector. These additional sources of uncertainty are most consistently accounted for within the Bayesian paradigm. The application of simulation-based inference (SBI) allows for the reconstruction of discharge parameters within a dynamic model, thereby taking a step towards creating a new method for studying the thunderstorm atmosphere – elveslocation. This work presents a dynamic model of an elve, which enables both the identification of characteristic spatiotemporal patterns of an event (generator mode) and the reconstruction of discharge parameters (SBI simulator mode).
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Earth and Planetary Astrophysics

Exoplanet System Architecture: Sculpting the Inner Regions

Mark R. Swain, Geoffrey Bryden, Jonathan C. Tan et al. (+14 more)

In this study, we seek to improve our understanding of the competing roles of disk-driven and planet-planet dynamical migration in sculpting planetary system architecture in the inner $\lesssim 1.5$ au of protoplanetary disks. Over a range of host star masses, we compare the orbit semimajor axis values of transiting multi-planet and resonant systems to observationally-derived estimates of protoplanetary disk inner truncation radius $R_{i}$, corotation radius $R_{co}$, and dust sublimation radius $R_{dust}$. We find that disk-driven migration is primarily responsible for setting the inner edge of planetary systems near $R_{co}$ and that subsequent dynamical migration shapes the distribution of planetary semimajor axis values over the range $\approx 20-300$ $R_{\star}$. If multi-planet systems form in a way similar to the resonant chain systems, either a zone of highly efficient planet formation at $\gtrsim 100 R_{\star}$, followed by subsequent disk-driven migration, is implied, or a modified in-situ mechanism operating over a region from $\simeq 15-100 R_{\star}$ and incorporating disk-driven migration is needed. There are indications that after disk dispersal, dynamical migration causes a subset of planets to migrate to locations inside $R_{co}$.
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All authors Mark R. Swain, Geoffrey Bryden, Jonathan C. Tan, Eric Gaidos, George Zhou, Caeley V. Pittman, Christopher M. Johns-Krull, Ann Marie Cody, Meredith A. MacGregor, Laura Venuti, Aayush Gautam, Neal Turner, Zhaohuan Zhu, Evgenya Shkolnik, Connor Robinson, Valerie Scott, John Arballo

Earth and Planetary Astrophysics

Spin-Orbit Alignment of Two Neptune-size Planets Younger than 500 Myr: TOI-560 b and TOI-5082 b

Elina Y. Zhang, Fei Dai, Andrew W. Howard et al. (+25 more)

Stellar obliquity measurements provide a direct probe of planetary system dynamics, but remain sparse for Neptune-size planets, particularly at young ages. We present Rossiter-McLaughlin measurements for two young Neptune-size planets, TOI-560 b and TOI-5082 b, using time-resolved Keck Planet Finder (KPF) spectroscopy and joint modeling with TESS transit photometry. We measure sky-projected obliquities of $\lambda_b = -25 \pm 16^\circ$ for TOI-560 b and $\lambda_b = 19^{+17}_{-13}{}^\circ$ for TOI-5082 b. Combining these constraints with stellar rotation periods and spectroscopic estimates of $v\sin i_\star$, we obtain 95% upper limits of $\psi < 69.7^\circ$ and $\psi < 50.5^\circ$, respectively. Both systems are therefore consistent with low-to-moderate true obliquities and show no evidence of strong spin-orbit misalignment. With ages of $480 \pm 190$ Myr for TOI-560 b and $180 \pm 9$ Myr for TOI-5082 b (a likely member of the CRIUS197 stellar association), the systems are in a key evolutionary phase when post-disk dynamical processes such as secular interactions may begin to manifest. Nevertheless, both systems remain consistent with low obliquity. In the broader context of young systems with existing measurements, these results support an emerging picture in which Neptune-size planets at $\lesssim 1$ Gyr are commonly found in low-obliquity configurations.
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All authors Elina Y. Zhang, Fei Dai, Andrew W. Howard, Samuel P. Halverson, Howard Isaacson, Ryan A. Rubenzahl, Huan-Yu Teng, Xian-Yu Wang, Songhu Wang, Daniel Hey, Daniel Huber, Benjamin J. Fulton, Jack Lubin, Luke B. Handley, Steven Giacalone, Erik A. Petigura, Lauren M. Weiss, Aaron Householder, Casey Y. Lam, Judah Van Zandt, Steve R. Gibson, Kodi Rider, Arpita Roy, Ashley Baker, Jerry Edelstein, Christopher L. Smith, Josh Walawender, Joshua N. Winn

Earth and Planetary Astrophysics · Cross-listed from astro-ph.IM

Automated Shape-Model-Based Astrometry of Phobos from Mars Express SRC Images

Wangxin Lai, Qingfeng Zhang, Rui Zhang et al. (+4 more)

High-resolution spacecraft images provide important astrometric constraints for orbit refinement, but measurements of resolved bodies are often limited by labor-intensive control-point selection and the difficulty of achieving consistent reductions over large image archives. We present an automated shape-model-based astrometric pipeline for Phobos and apply it to Mars Express Super Resolution Channel (SRC) images. For each exposure, a synthetic image is rendered from a high-resolution 3D shape model under the nominal spacecraft-target-Sun geometry. Feature correspondences between the observed and synthetic images are established using SuperPoint and SuperGlue, followed by RANSAC filtering. The matched synthetic-image keypoints are then associated with surface points through ray-shape intersection. The geometric adjustment fixes the adopted body orientation, spacecraft state, and corrected camera pointing and estimates only two effective plane-of-sky position offsets using the exact perspective-projection model. These offsets are used to derive the center-of-figure position of Phobos. We first test the method on an image set previously analysed with a control-point approach and obtain comparable astrometric performance. We then extend the analysis to a larger SRC dataset spanning 2007-2025 and obtain 1113 successful measurements. Relative to the JPL MAR099 ephemeris, the resulting observed-minus-computed residuals have mean values of 0.186 km in $\alpha \times cos(\delta)$ and 0.053 km in $\delta$, with corresponding standard deviations of 0.609 km and 0.583 km. These results demonstrate that the proposed pipeline provides a practical approach to large-scale, homogeneous astrometric reduction of archival spacecraft images of Phobos, with potential application to other resolved bodies.
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All authors Wangxin Lai, Qingfeng Zhang, Rui Zhang, Kai Tang, Chunyu Ding, Zhan Li, Haipeng Wang

Earth and Planetary Astrophysics

Assessment of the 5 August 2026 Falcon 9 Upper-Stage Lunar Impact: Energetics, Crater Scaling, and Comparison with LRO Observations

Mavia Anjum

The objective of this study was to characterize the human-made object that impacted the Moon on 5 August 2026, to estimate the dimensions of the crater it produced, and to compare the estimates with the crater subsequently measured by the Lunar Reconnaissance Orbiter (LRO). The impactor was the discarded upper stage of a SpaceX Falcon 9 rocket, which struck the surface near Einstein crater at a velocity of 2.43 km/s. The kinetic energy and linear momentum of the impactor were calculated, and the crater diameter was estimated using pi-group scaling relationships and measured rocket-body impacts as empirical analogs. The kinetic energy of the impactor was found to be 1.18 x 10^10 J, equivalent to approximately 2.8 tonnes of TNT. Compact-body pi-group scaling yielded a final rim-to-rim diameter of 46-57 m, and the empirical analogs yielded 26-27 m, leading to a pre-observation preferred estimate of 25 m within a range of 20-30 m. Between 11 and 12 August 2026, LRO imaged a crater approximately 18 m in diameter and less than 3 m deep. The results revealed that the compact-body scaling overpredicted the observed diameter by a factor of 2.6-3.2, whereas the empirical-analog method overpredicted it by 39-50%. When the nearest-mass analog was applied as a single crater rather than as a double crater, the estimated diameter was approximately 18 m, in close agreement with the observation. It was found that the hollow and elongated geometry of the stage, rather than a single equivalent bulk density, is the principal factor governing the crater size. This study provides a direct comparison of impact-scaling methods against a measured artificial lunar crater.
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Saturday 22 August

Earth and Planetary Astrophysics

A surviving pink spinel records an early aluminous melt on the ureilite parent body

Yaozhu Li, Phil J.A. McCausland, Roberta L. Flemming et al. (+2 more)

Ureilites are ultramafic achondrites interpreted as fragments of a differentiated parent body, yet their origin and evolution remain debated because textural equilibrium coexists with chemically primitive compositions. Here we report mineralogical, isotopic, and microstructural observations from polymict ureilite Elephant Moraine (EET) 87720. The sample contains unusually magnesian olivine (Mg# up to 98.7), Ca-poor pyroxene (Wo as low as 1.0), and rare coarse-grained pink aluminous spinel containing 56.4-58.7 wt% Al2O3 and 11.3-11.8 wt% Cr2O3. In situ triple oxygen isotope measurements of spinel and associated forsteritic olivine plot along the ~1-slope Carbonaceous Chondrite Anhydrous Mineral (CCAM) line, consistent with bulk ureilites. The clasts also follow the ureilitic Fe-loss/addition trend, with near-constant chondritic Mn/Mg ratios. These observations demonstrate that the clasts are indigenous to the ureilite parent body and extend the known ureilite oxygen isotope range to delta18O ~9.7 per mil. Three-dimensional dark-field X-ray microscopy reveals a hierarchical deformation microstructure in the spinel, comprising distributed lattice curvature, localized slip-band-like boundaries, and coherent mosaic-domain boundaries, indicating multiscale accommodation of shock-induced crystal-plastic deformation. We propose that the aluminous spinel crystallized from a locally Al-rich, Ca-poor melt under low oxygen fugacity. Al partitioning between coexisting spinel and olivine yields a crystallization temperature of 1318 +/- 43 K, consistent with a thermally elevated parent body. The spinel may therefore preserve a rare crystallization product of an early aluminous melt that has largely disappeared from the ureilite record, providing an archive of early planetary differentiation.
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All authors Yaozhu Li, Phil J.A. McCausland, Roberta L. Flemming, Noriko T. Kita, Carsten Detlefs

Friday 21 August

Earth and Planetary Astrophysics

Assessing the Impact of High-Resolution Imaging on Statistical Validation of TESS Planet Candidates

Michael Collier, Steven Giacalone, Brian Derfer et al. (+38 more)

High-resolution imaging is widely used to constrain false-positive scenarios in exoplanet validation, but it is a finite follow-up resource that reaches only a subset of candidates, and its population-level impact on validation outcomes has not been quantified through controlled removal experiments. Using an automated pipeline built on TRICERATOPS, we compute the false-positive probability (FPP) of 443 TESS planet candidates. For the 264 planet candidates with high-resolution imaging observations, we compute FPP with and without the corresponding contrast curves, allowing us to quantify the impact of the additional data. We find that 72% of 68 contrast-curve bearing validated planets would fail validation without their adopted contrast curves. The fraction requiring imaging decreases with increasing planet size, from 100% below $1.7~R_\oplus$ to $33\%$ above $4~R_\oplus$: within our sample and TRICERATOPS-based analysis, the availability of high-resolution imaging directly limits the yield of small-planet validation and the supply of validated targets for atmospheric characterization. Our analysis statistically validates 64 new TESS planets with sizes spanning 0.94 to 7.83 $R_\oplus$ across hosts of spectral type M through F. Four of these are highly amenable to JWST observations based on the transmission and emission spectroscopy metrics, and each achieves validation only with its imaging constraint.
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All authors Michael Collier, Steven Giacalone, Brian Derfer, David R. Ciardi, Catherine A. Clark, Ian J. M. Crossfield, Sarah Deveny, Sergio B. Fajardo-Acosta, Elise Furlan, Emily A. Gilbert, Steve B. Howell, Adam L. Kraus, Rachel A. Matson, Joshua E. Schlieder, Julian C. van Eyken, David Baker, Khalid Barkaoui, Özgür Baştürk, Mario Basilicata, Izuru Fukuda, Akihiko Fukui, Mourad Ghachoui, Michaël Gillon, Emmanuel Jehin, Jerome de Leon, Luigi Mancini, Francesca Manni, Gabriel Murawski, Bob Massey, Luca Naponiello, Norio Narita, Justus Randolph, Roberto Zambelli, Richard P. Schwarz, Abderahmane Soubkiou, Gregor Srdoc, Chris Stockdale, Toshi Suganuma, Jiaqi Wang, Francis P. Wilkin, Selçuk Yalç{\i}nkaya

Earth and Planetary Astrophysics

A Highly Reflective Atmosphere on the Lava World TOI-561b Revealed by JWST/NIRSpec Phase Curve

Samuel Boucher, Lisa Dang, Alex McGinty et al. (+15 more)

Ultra-short period (USP) rocky planets are expected to be depleted of any substantial gaseous envelope due to the intense irradiation they receive from their host star, making the recent detection of an atmosphere around TOI-561~b particularly surprising. That finding was based on the planet's bulk density and dayside emission spectrum, but full-orbit phase curve observations offer a more comprehensive way to constrain the presence and characteristics of a planet's atmosphere. In this paper, we map TOI-561~b's 3-5~$\mu$m emission using JWST/NIRSpec multi-orbit spectroscopic phase curves, explicitly accounting for the curvature of the out-of-eclipse baseline and possible hotspot offsets. From a simple energy balance argument as well as comparing to general circulation models, we find the phase curve observations are best explained with high Bond albedo and moderate global heat transfer. Our 37-hour continuous observation provides a long baseline that allows us to model stellar granulation, the planetary phase curve, and dayside emission simultaneously, effectively disentangling these signals and yielding a dayside emission spectrum that is more robust against stellar variability and consistent with previous eclipse-only fits. Using general circulation model outputs, we constrain where clouds can plausibly form and test candidate compositions, finding that silicate clouds, such as SiO$_2$ and MgSiO$_3$, can form on the dayside near the terminator and explain the observed albedo. Our findings confirm that TOI-561~b appears to have a global reflective atmosphere, suggesting exchange of volatiles with the interior to maintain it.
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All authors Samuel Boucher, Lisa Dang, Alex McGinty, Johanna K. Teske, Raymond Pierrehumbert, Anjali A. A. Piette, Nicole L. Wallack, Angharad Weeks, Neil T. Lewis, Tim Lichtenberg, Mykhaylo Plotnykov, Emma Postolec, Daniel Huber, Timothy R. Bedding, Harrison Nicholls, Bo Peng, Mark Hammond, Diana Valencia

Earth and Planetary Astrophysics · Cross-listed from astro-ph.IM

NestyNet. IV. Laws Chosen by Nothing in Advance

Rodrigo Ibata, Wassim Tenachi, Foivos Diakogiannis et al. (+2 more)

Differential-equation (DE) discovery tends to break down precisely where much of physics begins. Fields are coupled, governing laws are nonlinear in the state, amplitudes, coordinates, or operators of interest, yet derivatives must remain consistent across fields, channels, and differentiation orders. NestyNet-DE addresses this via two complementary DE search strategies, both employing analytic derivatives from segmented neural surrogates: a sparse-library route linear in the outer coefficients, and a new operator-factorized route that searches directly over equation structure rather than a fixed library, recovering compositional laws the sparse route misses. The recovered laws can be strongly nonlinear in states, fields, coordinates, and their couplings. The framework also handles multi-dataset shared-support discovery, complex and vector laws, and Hamiltonian discovery from phase-space trajectories. Beyond a law's form, the same data yield its geometry, the Lie point symmetries of the recovered equation. We apply the pipeline to 30 years of daily ephemerides of $308$ main-belt asteroids and recover the reduced-Kepler hierarchy (areal law, inverse-square force, and reduced Hamiltonian), where a discovered rotational symmetry fixes the centrifugal coefficient rather than fitting it. We also present a benchmark of 57 real-valued ODEs and 26 complex-valued systems, including the Schrödinger and Dirac equations, with Maxwell's equations as a coupled vector-PDE case study. Here, discovery is not shackled to a fixed library, nor does it end at the equation. It composes laws that no dictionary anticipated, and closes the loop from data, to a law chosen by nothing in advance, to the geometry that explains and integrates it.
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All authors Rodrigo Ibata, Wassim Tenachi, Foivos Diakogiannis, Neil Ibata, Anirudh Shankar

Earth and Planetary Astrophysics

Does Cumulative XUV Unify the Neptunian Desert?

Qunfeng Jiang

The Neptunian desert is the scarcity of roughly $2$-$10\,R_{\oplus}$ planets on orbits of a few days. Atmospheric escape driven by stellar X-rays and extreme-ultraviolet (XUV) radiation may shape its lower boundary by stripping hydrogen-helium envelopes. Because M dwarfs and F-, G-, and K-type stars have different activity histories, present bolometric irradiation may not trace the cumulative high-energy dose that drives escape. We ask whether cumulative XUV yields a common boundary across spectral type and whether the convergence survives star-to-star variation in age and rotation. Using 1850 Kepler and TESS planets, Model for Rotation of Stars (MORS) activity tracks, and a global boundary model, we find that the offset between M dwarfs and FGK stars shrinks from $-1.065$ dex in bolometric flux to $-0.369$ dex for a common 5 Gyr median-rotation XUV history. Assigning plausible ages and initial rotations to individual hosts preserves the smaller XUV offset in every trial, with a median reduction of 69.1%. A common-period null yields comparable alignment. Cumulative XUV therefore substantially reduces the host-type dependence, but the present data do not establish a universal XUV threshold independent of orbital period.
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Earth and Planetary Astrophysics

Transit Searches for Habitable-Zone Exoplanets with Artificial Intelligence

Qingtian Liu

Searching for Earth-sized planets in stellar habitable zones ultimately means finding a small number of very shallow, widely separated transits in noisy light curves. Around Sun-like stars, habitable-zone planets generally have long orbital periods, so a finite observing baseline may record only a few transits. At the same time, intrinsic stellar variability, instrumental systematics, and data gaps can obscure these weak events or produce transit-like brightness changes. This review examines recent progress in AI-assisted light-curve preprocessing, weak-signal searches, candidate vetting, and parameter inference, and considers the potential roles of pretraining and multimodal models. Taken together, the studies reviewed here show that AI has practical value in making large-scale light-curve analysis more efficient, recovering more signals at low signal-to-noise ratios in some injection tests, and reducing the number of targets requiring manual review. This review concludes that combining AI with physical modeling, statistical inference, and follow-up observations provides a practical route to improve both the discovery efficiency and the reliability of habitable-zone candidate studies.
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Earth and Planetary Astrophysics

The impact of tidal locking on Earth-like planetary dynamos

J. P. Hidalgo and D. R. G Schleicher

We investigate how tidal locking affects the planetary dynamo and the magnetospheres of Earth-like planets orbiting the habitable zones of M dwarfs. We couple an empirical stellar wind model with two distinct planetary dynamo paradigms, direct rotational scaling and energy-flux scaling, using a Constant Time Lag (CTL) model to simulate continuous tidal spin-down until synchronization. We model two hypothetical planets based on a highly dissipative Modern Earth and a less dissipative, rapidly rotating Early Earth representative of the Paleoarchean. Our results show that tidal locking acts as a severe negative feedback on planetary magnetism across both paradigms, where the dipolar field frequently collapses before full tidal synchronization is reached. Essentially, a shielded atmospheric environment around M dwarfs requires a host massive enough ($\geq 0.32 M_\odot$) to place the HZ at wider orbital distances, sparing the planet from the sub-Alfvénic environment, and the internal tidal dissipation of the planet must be sufficiently low to prevent rapid rotational decay. For mid-to-late M dwarfs, the inevitable tidal locking and the extreme stellar wind pressures result in a total collapse of the magnetic shield, reducing the likelihood of atmospheric protection to essentially zero across the habitable zone.
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Earth and Planetary Astrophysics · Cross-listed from astro-ph.IM

Chang'e 7 Lunar Lander Optical Camera-Telescope: Optical Astronomy from the Moon

Quentin Andrew Parker, Partha Sarathi Pal, Junhao Chen et al. (+8 more)

We report the design and manufacture of a new, lightweight, wide-field, optical camera-telescope on board the Chang'e 7 lunar mission (launched in August 2026 and due for lunar touchdown in late November 2026). The camera is capable of static, panchromatic imagery within a $420-696~nm$ optical wavelength range. The camera was designed and built under the small lunar astronomy observation station program of the Chinese National Space Agency (CNSA) as a collaboration between the International Lunar Observatory Association of Hawaii (ILOA), the Laboratory for Space Research (LSR) of the University of Hong Kong (HKU) and the Beijing Institute of Space Mechanics and Electricity (BISME). The camera has been built to meet science goals of the mission for sustainable astronomical operation over a large range of temperatures from the Moon's south pole. We report on the design and ground based preliminary performance, together with an analysis of the camera's simulated output to indicate the range of astronomical observations possible from the lunar surface given the camera's limited sensitivity and angular resolution given the modest aperture and wide field of view.
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All authors Quentin Andrew Parker, Partha Sarathi Pal, Junhao Chen, Meng Su, SeyedAbdolreza Sadjadi, Andreas Ritter, Andy C. T. Kong, Zhengjie Tian, Haoyang Yuan, Suijian Xue, Steve Durst

Earth and Planetary Astrophysics

Microwave Remote Sensing of Giant Planet Atmospheres: Considerations for Saturn and Uranus Orbiter Missions

Alex Akins and Mark Hofstadter

Microwave radiometer instruments are uniquely capable of studying volatile element abundances and heat/mass transport within the deep atmospheres of giant planets. The results of the Juno MWR experiment have challenged long-held assumptions regarding Jupiter's troposphere, and the inclusion of such an instrument on future missions to Saturn or the ice giants would similarly re-write our understanding of giant planet atmospheres. We present a high-level summary of the capabilities of microwave radiometers for the study of giant planet atmospheres, including a review of the various scientific motivations and current knowledge, concise statement of the fundamentals of radiometer remote sensing accessible at the systems-engineering level, and calculations which are of illustrative value in the design of future instruments.
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Earth and Planetary Astrophysics

Physics-Informed Bayesian Optimization Warm-Starts for Sequential Convex Programming in Asteroid Surface Hopping

Baran Ekşi and Tufan Kumbasar

Surface hopping is an attractive mobility mode for small-body exploration, but designing fuel-optimal hops on asteroid 433~Eros requires solving a nonconvex optimal control problem with an irregular polyhedral gravity field, thrust–mass coupling, and collision-avoidance constraints. We show that a physics-informed Bayesian Optimization (BO) warm-start—a Gaussian-process search over a single Bézier control point that requires no offline training—provides a more reliable initialization for Sequential Convex Programming (SCP) than the standard straight-line guess. The straight chord penetrates the asteroid on every inter-site transfer considered here and degrades convergence. The physics-informed BO reference feeds an SCP stage in which a log-mass change of variables convexifies the thrust–mass coupling and nearest-facet half-spaces enforce collision avoidance, and an automated Pareto time-of-flight sweep selects fuel-priority solutions without introducing bilinear terms. Applied to all 20 ordered transfers among five representative surface sites and validated under 10 random seeds, the framework tracks every trajectory to meter-level terminal accuracy in closed-loop Monte Carlo simulation, completes a five-site tour for one fifth of the propellant budget, and reduces mean $\Delta V$ by roughly one third relative to an idealized two-impulse ballistic trajectory estimate. A straight-line ablation credits the warm-start with cutting the mean SCP iteration count from 8.8 to 5.9 and removing the one convergence failure. A target-perturbation analysis further shows that the solutions vary smoothly with the landing target, with no jumps between local basins.
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Earth and Planetary Astrophysics

Accounting for Transit Timing Detectability: Biases in Planetary Radius and Orbital Period

Skylar D'Angiolillo, Daniel Fabrycky and Mariah G. MacDonald

Transit Timing Variations (TTVs) are deviations from the time an observer would expect to see an exoplanet transit its host star. In multi-planetary systems, significant TTVs may indicate the presence of another body in the system gravitationally interacting with the transiting exoplanet. T. Holczer et al. (2016) catalogs 2599 Kepler Objects of Interest (KOIs) and provides a statistical analysis of their TTVs for candidates that have transited at least seven times. However, this conservative limit on the number of transits neglects long-period KOIs. Therefore, we extend the statistical analysis performed by T. Holczer et al. (2016) to the population of KOIs that have between three and six transits. We identify six KOIs, three of which have Kepler names (Kepler-103 c, Kepler-90 g, and Kepler-1662 c), with significant TTV signals that were originally overlooked by T. Holczer et al. (2016). Additionally, we search for trends regarding the planetary radius and orbital period of KOIs with significant TTVs. Through a survival analysis, we determine that planets with shorter orbital periods require larger TTV signals to be detected compared to longer period planets, regardless of planetary size. Uncovering trends in TTV statistics such as this one will provide targets for future forward modeling of planetary architectures.
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Thursday 20 August

Earth and Planetary Astrophysics

JWST Spatial-Spectral Mapping of Green Comet C/2022 E3 (ZTF)

Stefanie N. Milam, Nathan X. Roth, Geronimo L. Villanueva et al. (+9 more)

We report a survey of molecular emission from cometary volatiles using the James Webb Space Telescope (JWST) toward Oort cloud comet C/2022 E3 (ZTF) carried out on UT 2023 February 28 and March 1 at a heliocentric distance (rH) of 1.33 au. These measurements of H2O, HCN, CH3OH, C2H6, CH4, CO, CO2, 13CO2, and OCS sampled post-perihelion molecular chemistry in C/2022 E3. A suite of near to mid-infrared OH (prompt emission) transitions were also detected. This work presents nucleus-centered spectra for all detected species, spatial-spectral maps of column density and rotational temperature as a function of distance from the nucleus for all except C2H6, HCN, and OH, and maps of co-measured continuum. The spatial distributions of both quantities were anisotropic for all mapped molecules; however, H2O showed distributions distinct from the remaining species. Coma-averaged values of the ortho-to-para ratio (OPR) for H2O and the 12CO2/13CO2 ratio derived from these maps were consistent with the statistical equilibrium value of 3 and the terrestrial value of 89, respectively. The modeled mass fraction of the sub-micron dust grains is dominated by amorphous carbon (56%) followed by amorphous Mg:Fe pyroxene (28%), crystalline olivine (10%), and amorphous Mg:Fe olivine (5%) with a crystalline mass fraction of 0.2385(0.0008). We compare the volatile and dust composition of C/2022 E3 (ZTF) against comets measured to date, including those surveyed by JWST.
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All authors Stefanie N. Milam, Nathan X. Roth, Geronimo L. Villanueva, Dominique Bockelee-Morvan, Jacques Crovisier, David E. Harker, Michael S.P. Kelley, Kiernan D. Foster, Ian Wong, Davide Farnocchia, Marco Micheli, Heidi B. Hammel

Earth and Planetary Astrophysics

Effects of Outer Giant Planets on In Situ Formation of Inner Super-Earths

Phoebe Sandhaus, Rebekah I. Dawson, Mariah G. MacDonald et al. (+2 more)

Recent studies have found an observational correlation between the presence of outer giant planets and inner super-Earths, which implies that outer giants do not suppress the formation of super-Earths. We simulate late-stage in situ planet formation in the presence of outer giant planets using $N$-body simulations. We investigate the effects of two sets of outer giants: the four Solar System giant planets and three dynamically active giant planets. Compared to systems without outer giants, we find that systems with the Solar System giants tend to form inner super-Earths that are more compact, coplanar, and circular, while the systems with the dynamically active giants form inner super-Earths that are more eccentric, inclined, and widely spaced, with lower intrinsic multiplicity. Including a contribution from systems that form with dynamically active giant planets allows us to match observable quantities of super-Earths, including their two component eccentricity distribution. However, matching the observed population requires different formation conditions prior to the giant impact stage for systems with vs. without giant planets. In our model, observed super-Earths that form in the presence of dynamically active outer giants emerge from disks with lower solid surface densities and without a depleted gas stage, suggesting that the giant planets may have reduced, but not prevented, delivery and/or accretion of solids in the inner disk. With a large enough sample of inner and outer systems, we could break down occurrence rates of inner super-Earths based on the properties of outer giants, and vice versa, and then compare these conditional probabilities with simulations.
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All authors Phoebe Sandhaus, Rebekah I. Dawson, Mariah G. MacDonald, Cody J. Shakespeare, Sarah Morrison

Earth and Planetary Astrophysics · Cross-listed from astro-ph.IM

High-contrast aperture masking interferometry: detecting companions within the diffraction limit

Benjamin Calvin, Michael Fitzgerald and Jessica Castellanos

The pursuit of the direct discovery and characterization of Earth-like exoplanets has motivated high contrast imaging surveys using coronagraphs with narrow inner working angles. Traditional imaging methods, however, are limited by the size of the on-axis PSF and typically only detect companions at angular separations of > 2$\lambda$/D. Meanwhile, non-redundant masking (NRM) techniques have been used with single-aperture telescopes to interferometrically resolve astrophysical features at angular scales within the diffraction limit, but NRM interferometry faces sensitivity issues for high-contrast objects. In this project, we investigate utilizing high contrast coronagraphy in conjunction with NRM interferometry. We conduct a preliminary investigation of this combined architecture with the goal of determining the potential bounds of performance and discovery space for high-contrast targets within the inner working angle of traditional high-contrast imaging. We predict an improvement in the achievable contrast for photon-limited observations by combining the techniques, and we also develop estimates for wavefront stability requirements for the system.
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Earth and Planetary Astrophysics

Leveraging Impact Parameter to Mitigate the Transit Light Source Effect: Early Insights from TRAPPIST-1

Ana Glidden, Alexander I. Shapiro, Sara Seager et al. (+19 more)

Stellar activity complicates exoplanet transmission spectra, particularly for smaller planets around M dwarfs with JWST. The transit light source (TLS) effect, the imprinting of spectral differences between the average stellar disk and the occulted transit chord onto the transmission spectrum, makes it challenging to directly use the out-of-transit spectrum to correct for stellar contamination. Theory and observations suggest that spots may concentrate towards higher latitudes when the Coriolis force is substantial relative to buoyancy, leaving the equatorial region relatively quiet. Here, we evaluate how the latitudinal distribution of active regions shapes the strength of the TLS effect for planets spanning a range of impact parameters ($b$), using TRAPPIST-1 as a testbed. We first construct a fiducial model to illustrate two distribution regimes. With our model, the moderate-$b$ outer TRAPPIST-1 planets (f, g, h) occult a more typical region of the stellar disk than the inner planets and are thereby less affected by the TLS effect, though their bias may vary more from visit-to-visit as these active regions evolve with time. More generally, our results imply an impact parameter "sweet spot" for atmospheric characterization, independent of the sign of the active region temperature contrast, whose location depends on the distribution of active regions. The distribution may be revealed by transit residuals as multiple planets probe different latitudes, while longitudes are sampled in time, such that the variance and frequency of the correlated scatter could constrain active-region filling factors, sizes, and separations.
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All authors Ana Glidden, Alexander I. Shapiro, Sara Seager, Nadiia Kostogryz, Valeriy Vasilyev, Roeland P. van der Marel, Julien de Wit, Benjamin V. Rackham, Prajwal Niraula, Natalie H. Allen, Jingcheng Huang, Nikole K. Lewis, Zifan Lin, Jacob Lustig-Yaeger, Ryan J. MacDonald, Brett M. Morris, Elijah Mullens, Kevin B. Stevenson, Jeff A. Valenti, Daniel Valentine, Hannah R. Wakeford, C. Matt Mountain

Earth and Planetary Astrophysics · Cross-listed from astro-ph.IM

A Multi-instrument Generalized Lomb-Scargle Periodogram Implementation

Giulia Martos, Néstor Espinoza and Jorge Meléndez

We present an implementation of the well-known and broadly used Generalized Lomb-Scargle Periodogram (GLS) which simultaneously takes into account individual offsets introduced in the data by different instruments: a "multi-instrument" GLS periodogram. While the algorithm itself is not new, the simple closed form implementation we provide, to our knowledge, is. We showcase an application of our multi-instrument GLS on radial-velocity data of the hot Jupiter TOI-481 b, whose period is recovered with a higher significance compared to the standard GLS approach. The code is available on GitHub.
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Earth and Planetary Astrophysics · Cross-listed from physics.plasm-ph

Effect of ion temperature on lunar photoelectron sheath

Trinesh Sana and Sanjay K. Mishra

Observations suggest that the solar wind ions impinging on the lunar surface possess a finite temperature. The effect of ion temperature on the plasma sheath over the lunar surface is investigated in this paper. To account for thermal effects, a thermal pressure term has been added to the ion-flow force equation. Quantitative estimation of sheath characteristics has been performed by solving the Poisson equation, accounting for photoelectrons, solar wind electrons, and warm ions. Notably, the presence of warm ions within the sheath, i) changes the potential, field, sheath population density structures, ii) changes the sheath thickness, iii) reduces the photoelectron trapping, and iv) reduces solar wind electron reflection, compared to cold ions. The effect is more prominent at high lunar latitudes, which in turn may significantly modulate the dust dynamics.
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Earth and Planetary Astrophysics

Quasi-diurnal Kelvin Wave Observed in the Atmosphere of Mars by the Pressure Sensor on the InSight Lander

Anzu Asumi, Jorge Hernández-Bernal, Kaoru Sato et al. (+1 more)

During the initiation phase of Martian dust storms, a spectral signature of a zonal wavenumber 1 normal mode Kelvin wave (K1) has been observed in several surface pressure records. However, the K1 signal has not been extracted directly since its eigenfrequency is close to that of the diurnal tide, making their separation difficult. We apply singular spectrum analysis to more than one Martian year of InSight surface pressure observations, including the MY34 C dust storm (C34). This analysis enables us to directly extract the transient K1 signal. Clear K1 signals appear during the Northern-Hemisphere spring and autumn with the average amplitudes of around 2 Pa. They reach 8 Pa during the C34 storm, which is substantial compared with a simultaneous diurnal signal (S1) maximum of 39 Pa. Near the peak time, K1 and S1 are in phase, and unexpectedly the S1 period shortens to 23.5 Mars hours. Subsequently, K1 rapidly decays and the S1 period recovers to 24 Mars hours. The phase relation between K1 and S1 as well as the S1 period shortening indicates that a resonance occurred between S1 and K1. Comparison with simulations at the model grid point closest to the InSight landing site shows that the Mars Planetary Climate Model realistically reproduces the observed characteristics of the surface pressure variations.
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All authors Anzu Asumi, Jorge Hernández-Bernal, Kaoru Sato, Aymeric Spiga

Earth and Planetary Astrophysics

Origin of nucleosynthetic isotope variability in the NC reservoir: Evidence from Ti, Cr, and Mo isotopes

Elias Wölfer, Christoph Burkhardt, Gerrit Budde et al. (+3 more)

Nucleosynthetic isotope anomalies allow distinguishing between non-carbonaceous (NC) and carbonaceous (CC) type meteorites, and have revealed correlated isotope variations especially among NC bodies. Understanding the origin of this NC trend is important for identifying the processes that produced the NC isotope heterogeneity, and for using these isotope anomalies to reconstruct the early evolution of the solar protoplanetary disk. We report mass-independent Ti, Cr, and Mo isotope compositions for a comprehensive set of previously not or only poorly investigated meteorites, as well as acid leachates obtained from the sequential digestion of primitive ordinary chondrites. Some of the samples investigated in this study fill previously identified apparent gaps in the NC trend, suggesting these gaps reflect unrepresentative sampling of a more continuous isotopic trend. Bulk meteorites and leachates exhibit distinct isotope systematics, indicating that the NC isotope variability does not reflect selective thermal processing of presolar carriers in the disk. The NC trend also cannot reflect the continuous addition of CC dust from the outer to the inner disk, because early- and late-formed NC meteorites display largely overlapping isotopic compositions. Instead, we find that the NC isotope heterogeneity is best accounted for by fractionation and mixing among chemically and isotopically distinct dust components, similar to the processes that produced the isotopic variability among carbonaceous chondrites. On this basis we argue for the presence of substructures in the inner disk, which facilitated fractionation and mixing among distinct dust components, and helped preserve a long-lived dust reservoir from which NC planetesimals accreted over an extended period of time.
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All authors Elias Wölfer, Christoph Burkhardt, Gerrit Budde, Christian A. Jansen, Jonas Pape, Thorsten Kleine